The present invention relates to a ball coupling suitable for use in particular in circuits for conveying pressurized fluid for the purpose of providing a quick coupling between two elements of the circuit such as a pipe and a member for delivering or receiving fluid, or such as two pipes.
Ball couplings are known which comprises a male tubular endpiece having an outer annular collar, and a female tubular endpiece for receiving the male tubular endpiece, the endpieces being designed to be associated with respective circuit elements. The male endpiece is held in the female endpiece by locking means pressing balls into abutments behind the annular collar.
In general, the locking means comprise a ball-holding cage mounted on one end of the female endpiece so as to extend it axially, and a thimble mounted on the ball-holding cage so as to be capable of moving axially between a first position and a second position. The thimble has internal camming surfaces that are axially offset relative to one another and that are organized in such a manner that when the thimble is in its first position, the balls are held so as to project into the inside of the cage, thereby retaining the annular collar on the male endpiece, and so that when the thimble is in its second position, the balls are released radially, thereby enabling them to co-operate with the annular collar so as to be moved from the projecting position to a retracted position, thereby enabling the male endpiece to be withdrawn.
Such ball couplings are in widespread use in industry because they make it possible to achieve coupling quickly. In addition, coupling is simple to perform and can be implemented by unspecialized labor. However, when a traction force is applied on one of the coupled-together elements, there is a risk of the thimble coming into abutment against some other element located close to the coupling, and thus a risk of it being moved axially relative to the ball-retaining cage. If the circuit is under pressure, such displacement can lead to the pipe becoming suddenly disconnected which is equivalent to the pipe rupturing, and in addition this can happen with a xe2x80x9cwhiplashxe2x80x9d effect that increases with increasing pressure of the fluid in the circuit.
There thus exists a need, that has not been satisfied in convenient manner until now for a ball coupling that limits the risk of a coupled pipe being disconnected accidentally.
To this end, the invention provides a ball coupling having a longitudinal axis and comprising a male tubular endpiece provided with an outer annular collar, a female tubular endpiece on which one end of a tubular sleeve is fixed coaxially, the sleeve extending beyond the female endpiece and having slots to form a cage for retaining balls for locking the male endpiece in a coupled state in the female endpiece, and a thimble that is coaxial about the sleeve and that is mounted thereon via guide means enabling the thimble to be guided so as to turn about the longitudinal axis of the coupling and enabling the thimble to turn through a turn angle relative to the sleeve between a first position and a second position, the cage having internal means for receiving locking balls in a connected state, said means presenting, for each ball, a first recess extending in register with the corresponding slot when the thimble is in its first position so as to form an abutment for holding the corresponding ball in a position where it projects into the inside of the sleeve so as to define a passage of section smaller than that of the outer annular collar, and a second recess connected to the first recess via a sloping wall and offset from the first recess by an angle corresponding to the turn angle so as to receive the corresponding ball in a retracted position that is retracted relative to its projecting position so as to define a passage of section that is not less than the section of the outer annular collar, when the thimble is in its second position.
Thus, the coupling is unlocked by causing the thimble to turn relative to the sleeve. The risk of that movement occurring for accidental reasons is small. The probability of the coupling becoming unlocked accidentally is therefore reduced.
In a particular embodiment, the slots are elongate and extend parallel to the longitudinal axis of the coupling, each first recess extending in register with a portion of a slot that is adjacent to the free end of the sleeve.
In an advantageous variant, a valve member is mounted in the female endpiece to move between a closed position for closing the female endpiece, into which position it is urged resiliently, and an open position into which it is moved by the male endpiece when it is in a position inside the female endpiece corresponding to the coupled state; the sleeve has slots for forming a cage for holding retaining balls for retaining the male endpiece in a disengaged position relative to the female endpiece, the retaining balls extending relative to the locking balls in a position that is offset axially towards the free end of the sleeve, the thimble being mounted on the sleeve so as to be movable into a third position and having internal means for receiving the retaining balls such that the retaining balls are in a position in which they project into the inside of the sleeve so as to define a passage of section smaller than that of the outer annular collar, at least when the thimble is in its second position, and such that the retaining balls are in a retracted position that is retracted relative to their projecting position so as to define a passage of section that is not less than the section of the annular collar when the thimble is in its third position, and the coupling has means for putting the male endpiece when in the disengaged position into connection with an exhaust.
Thus, prior to disconnection, the circuit associated with the male endpiece can be purged by bringing the male endpiece into the disengaged position. The risk of a disconnection being associated with a xe2x80x9cwhiplashxe2x80x9d effect is thus very low.
Advantageously, the thimble has an additional annular recess connected via a sloping wall to the first recesses so as to extend in register with portions of the slots extending close to the fixed end of the sleeve for receiving the balls in the retracted position, the ring being slidably mounted in the additional recess so as to slide between a position for disengaging the additional recess and a position for obstructing the additional recess, into which position the ring is urged resiliently to push the balls into the first recesses.
Thus, the male endpiece is coupled merely by being inserted into the sleeve until the balls pushed away by the annular collar are retracted into the additional annular recess and, after the annular collar has gone past, return into the first recesses and thus into the projecting position under drive from the resilient return of the ring into its obstruction position. The coupling operation can thus be performed quickly and is particularly simple.